The present invention generally relates to a pattern position recognition apparatus which is adapted to effect position recognition of complicated IC chip patterns bonded on a basic plate constituting an electronic circuit.
In recent years, pattern position recognition has been effected using two patterns of images in a non-contact arrangement.
This conventional pattern position recognition technique will be described hereinafter with reference to the drawings.
FIG. 4 is a block diagram of the conventional pattern position recognition apparatus.
Referring to FIG. 4, an illuminating unit 23 is set to illuminate an object 22 which has the patterns to be recognized and which is placed on a positional table 21. A television camera 24 is set on a movable television camera support position 25. The television camera 24 is controlled by a television camera controlling circuit 26.
The image signals output from the television camera 24 enter an analog/digital conversion (hereinafter referred to as A/D conversion) circuit 27, where they are numerically encoded into image data of 0 through 255 gradation levels, and the image data are then inputted into a microcomputer composed of a CPU, a ROM, a RAM, input, output ports and so on.
The pattern position recognition apparatus is composed of a decision controlling circuit (CPU) 28 which is provided with instructions by a major controller or an operation panel, a binary-coded controlling circuit 29 for controlling the conversion of the input images into binary values, a window frame controlling circuit 30 for setting as a window frame a two-dimensional range to be processed with respect to the input images, a partial template cutting circuit 31 for successively cutting partial two dimensional patterns as a template from the binary-coded images within the window frame, a target template memory circuit 32 for previously storing as a target template the patterns to be recognized, a template comparing circuit 33 for comparing the cut partial template with the target template stored previously, and a representative position detecting circuit 34 for detecting the representative position of the template when the template has been determined to be a partial template which most coincides with the target template according to the template comparing circuit 33. The recognized result is fed into a main controller.
The operation of the pattern position recognition apparatus constructed as described hereinabove will be described below.
As shown in the flow chart of FIG. 5, an object 22 having patterns to be recognized is placed on a positional table 21 or the like. The focusing of the television camera 24 is set, and one picture is inputted (step 21). The images inputted are converted to binary (step 22). The two-dimensional range to be processed is set as the window frame (step 23). The partial template is cut from within the two dimension pattern of the window frame (step 24). The exclusive OR of each picture element (bit) with respect to the target template stored previously is obtained for determining a coincidence therebetween (step 25). Step 24 and step 25 are performed with respect to the entire window frame interior. The position at the recognized point is detected as the representative position of the partial template, wherein the total of the exclusive OR is largest, being recognized (step 26). However, the control returns to step 21 when an error recognition is provided. The image inputs are effected to change the binary level and the subsequent control steps are effected again (step 27).
In the conventional construction as described hereinabove, the images are converted to binary so as to compare the coincidence thereof with the total sum of the exclusive OR of the bits of each image element of the partial template and the target template. The recognition accuracy is reduced if the binary code is operated at the same level, when the concentration of the input images has changed due to the illumination changes during the inputting of the images, due to the television camera sensitivity changes and so on. Therefore, the processing becomes complicated in that in the binary level control a change of the binary-coded level is effected. In addition, there is a problem in that the processing time is increased.